Heterosexism is a system of attitudes, bias, and discrimination in favor of opposite-sex sexuality and relationships. It can include the presumption that other people are heterosexual or that opposite-sex attractions and relationships are the only norm and therefore superior. Although heterosexism is defined in the online editions of the American Heritage Dictionary of the English Language and the Merriam-Webster Collegiate Dictionary as anti-gay discrimination or prejudice "by heterosexual people" and "by heterosexuals", respectively, people of any sexual orientation can hold such attitudes and bias, and can form a part of internalised hatred of one's sexual orientation. Heterosexism as discrimination ranks gay men, lesbians, bisexuals and other sexual minorities as second-class citizens